paleontology7: The rise of birds (v1.0)

In the essay on the rise of reptiles, I talked about the emergence of flying reptiles. This essay talks about the emergence of birds from dinosaurs. They did not emerge from flying reptiles. The first feathered dinosaurs that emerged were about 160 million years ago in the Jurassic period. The earliest bird emerged about 150 million years ago.  The oldest beaked bird emerged about 120 million years ago. Birds have feathers. They are warm blooded. They have very small tails. Their arms support their wings. They have a wishbone. They have air sacs. Feet are adapted for perching. Woodpeckers have further adaptations for climbing. Sea birds have less perching ability. The emergence of birds was a major evolutionary change. 

The evolution of birds differs from flying reptiles in two major areas. Birds survived the mass extinction event 66 million years ago. Flying reptiles did not. The reason is not completely clear. Secondly, Birds evolved from a flightless dinosaur. Starting in the late 1990’s, a large trove of small, feathered dinosaurs was found that were transitional. One find was a micro raptor. It likely was a glider. Another was a velociraptor. The consensus now is that feathers evolved in dinosaurs first before birds evolved. There are two theories why. One is that once some dinosaurs become warm blooded, feathers preserve body heat and help with incubating eggs. Another is that feathers helped identify species and advance courtship (think peacock).  

There are three hypotheses on how flight developed. One is ground up. The second is tree down. The third is incline assisted running. The ground up hypothesis is that dinosaurs evolved powerful arm movements to assist with ground running, and finally becoming so confident with leaps that flight became possible. The tree down hypothesis is dinosaurs first gained flight by jumping from trees and acquiring flight as an evolutionary mechanism to avoid fatal accidents from this method. The incline assisted running hypothesis is that dinosaurs run up steep or vertical inclines by flapping their arms, scaling greater inclines than possible through running alone. 

This essay explores the emergence of birds 150 million years ago.